1. Field of the Invention
The present invention relates to various types of mobile terminals having built-in speakers, such as mobile telephones, PHS (personal handyphone systems), other mobile information terminals and the like, and more particularly relates to the sound-emitting structure of a mobile terminal which is devised so that the output of the speaker can be emitted from a plurality of the surface parts of the case.
2. Description of the Related Art
For example, mobile telephones include mobile telephones that have a folding structure as shown in FIGS. 1 and 2. FIG. 1 is an external view which shows a mobile telephone in an open state. FIG. 2 is an external view as seen from the back, which shows the mobile telephone in a closed state. This mobile telephone 2 is constructed so that an operating part 4 and a display part 6 can be folded up by means of a hinge mechanism 8. A plurality of key buttons 10 such as character keys or the like are disposed in the operating part 4, and a microphone 14 is disposed on the inside of a sound intake hole 12. An LCD display 16 is disposed in the display part 6, and a receiver 20 is disposed on the inside of a sound emission hole 18. Furthermore, a sound emission hole 22 is formed in the back side of the operating part 4, and a speaker 24 is installed on the inside of this sound emission hole 22.
Such a mobile telephone 2 is ordinarily carried in a folded state as shown in FIG. 2. When a call arrives, a calling sound is emitted from the speaker 24. During communications, the mobile telephone is used in an open state as shown in FIG. 1, and communications sound is emitted from the receiver 20, so that this sound is heard by the user.
Prior patent documents relating to the sound emission structures of such mobile telephones and communications terminal devices include Japanese Patent Application Laid-Open Nos. 2003-60757 and 2003-134201.
In FIGS. 4 and 5 and the description of these figures in Japanese Patent Application Laid-Open No. 2003-60757, a mobile telephone terminal is disclosed which is devised so that two sound holes are formed in the front side of a display device part or an operating device part for an acoustic converter which is disposed in the display device part or operating device part for causing sound to be emitted on the back side of the terminal, and the voice sound that is emitted from the sound emission surface of this acoustic converter is emitted from the sound holes on the display surface so that this sound can be heard by the user.
Furthermore, in Japanese Patent Application Laid-Open No. 2003-134201, a structure of a mobile telephone in which a sound hole is formed in the side surface part of a housing that covers the back side of a speaker, and a calling sound is emitted from the side surface part of the close housing, is disclosed as a structure that allows the calling sound to be sufficiently heard even when the housing is closed.
In cases where not only a calling sound but also communications sound is output from the speaker 24, for example, in cases where the mobile telephone is used as a hands-free device or the like, if the mobile telephone is placed on a desk top to block the sound emission hole 22, the sound volume of the communications sound will be reduced so that the communications sound becomes difficult to hear and, accordingly, the degree of understanding and degree of clarity will drop. Furthermore, if the sound emission hole 22 is blocked, the level of the calling sound drops.
In regard to such problems, it is conceivable to use a configuration in which a speaker is disposed on the side of the key buttons 10 of the operating part 4 separately from the speaker 24 used for the calling sound, and communications sound is output from this separate speaker. However, the disposal of such a speaker requires a switching mechanism that switches the two speakers according to the mode of use, so that the structure of the mobile terminal such as a mobile telephone or the like is complicated, thus hindering a reduction in the size and weight of the mobile terminal. In regard to this problem, in the case of the sound-emitting structures disclosed in the abovementioned patent documents, a calling sound can be emitted from the front and side of the case and heard by the user without installing a separate speaker.
However, in cases where the speaker disposed inside the case of a mobile terminal such as a mobile telephone or the like is large relative to the size of the case, although calling sounds or the like can be emitted by forming a sound emission hole adjacent to the speaker or in the case that covers the back side of the acoustic converter as in the techniques described in the abovementioned patent documents, a sufficient sound emission output cannot be obtained in such a simple sound emission structure in which a sound emission hole is simply formed in the case, if the size of the speaker is reduced and the density of the mounted parts to the mobile terminal is increased. If the wiring boards and the like disposed inside the case hinder the emission of sound and the sound is diffused inside the case, this causes a reduction in the sound emission output to the outside of the case, and there is a danger that this will cause a deterioration of the degree of understanding and degree of clarity in the communications voice sound having a different band than the calling sound. These problems are not disclosed in the abovementioned patent documents and cannot be solved by the techniques disclosed in these references.